1. Field of the Invention
The present invention relates to a focused ion beam machining method for obtaining by use of focused ion beam apparatus the cross-section or profile of a specimen, and also relates to a machining apparatus adaptable for use therewith. Generally, the specimen profile is for use in observation and analysis.
2. Description of Related Art
A typical focused ion beam machining method employing such focused ion beam apparatus to obtain the profile of a specimen is disclosed in, for example, Japanese Laid-open Patent Application, Tokkaisho 62-174918. The method disclosed therein is designed to first determine a rectangular region to be machined in a manner such that a specified portion being machined to have a desired cross-sectional pattern is aligned in position with one side of an ion beam scanning irradiation region. Then, irradiation of an ion beam onto the to-be-machined region gets started causing the to-be-machined region to become narrower with time in the sub-scanning direction. One feature of the prior known method is that the specimen may be etched most deeply at its specified portion whereat the intended profile is to be formed, which is attainable by causing the profile formation portion to not change in one side thereof at this time.
Unfortunately, during such profile formation, once-etched materials can badly behave to again attach or "re-attach" to surfaces of the specimen at those locations in or near the machining region, resulting in contamination of the cross-section of interest to be obtained. The prior art method taught by the above-identified Japanese document is designed so that the machining region becomes smaller gradually and thus is associated with a serious problem that reattached materials can be deposited in the previously machined region. Another problem faced with the conventional method is that such unwanted deposition would result in inability to accurately perform the profile observation and/or analysis required.
It is therefore an object of the present invention disclosed and claimed herein to avoid the problems encountered with the prior art and to enable achievement of machining of a specimen with less risk of reattachment within a shortened time period.